Reflector for rays emitted by alpha luminous source



April 29, 1930. J.'L. PEcH y 1,756,301

REFLECTOR FOR RAYSv EMITTED BY A LUMINOUS SOURCE Filed Nov. 14, 1927 wwwPatented Apr. 29, 1930 UNITED STATES JACQUES LOUIS PECH,0F MONTPELLIER,FRANC REFLECTOR FOR .RAYS EMITTED BY A LUMINOUS SOURCE Application ledNovember i4, 1927, Serial No. 233,277, and in France November 16, i926.

The invention relates to reflectors, the object of which is to confineWithin a limited space the maximum of rays emitted by a source of light.

The object of the invention is to provide a reliector wherein all of theluminous rays emitted by a source of light and impinging upon thereflector are reflected in such a way that they will all be combined orunited on the same side of a plane previously determined. y

In my invention I make use of mirrors of such form and arranged in sucha manner that the effect intended may be achieved. while'taking intoconsideration the dimensions of the source of light and the opticaldistortions of said mirrors, these distortions depending upon the shape,construction, and

material of these mirrors. l

The invention is applicable to installations or' apparatus for lightingpurposes which may be either stationary or movable.

The invention is illustrated on the accompanying drawing in which thesingle gure is a cross-sectional View of a reflector showndiagrammatically.

Assuming a source of light the maximum dimensions of which are comprisedbetween the points z', j, and k, for example the filament of an ordinaryelectric lamp; it is required to direct the greater part of therefiected rays from this source of light below a plane perpendicular tothe plane of the accompanying drawing indicated by the line D E parallelto the symmetrical axis Z m ofthe source of light. This is 'done asfollows. l

A reflector is constructed composed of mirrors situated on both sides ofthe .straight line or common axis D E, the said mirrors being made ofsilvered glass, polished metal or any other material generally used forthe manufacture of reflecting surfaces. The form or shapes of saidmirrors is determined by taking into consideration the variousparticulars hereinafter set forth.

It is necessary, in the first place, to know or determine experimentallythe order of magnitude of the optical distortions which may occur,according to the form, method of construct-ion and material comprisingthe refiecting surfaces proposed to be utilized. 1f, as assumedhereinafter, they are formed of beaten out brass which is silvered andpolished, it is necessary to vstate that such surfaces cannot be made bythe average workman or artisan working at radii of curvature presenting,between individual pieces worked or even for various points of the samepiece, variations to the extent of one millimeter.

This is why the rectangle Z m n ois shown on the drawing four apices ofwhich arc distant at least two millimetres from the source of light z'y' lo. i

Above the source of light is placed a parabolic mirror p q of silveredand polished brass the optical axis of which coincides with the line D Eand the focus of which is at o. Theoretically and practically, all thelumiL nous rays, the ray 7c q, 'for example, emitted by the source oflight z' y' 7c impinging upon any point of the mirror p q will bereflected so that they will approach the optical axis of this mirror.Starting from this point 72, if it be desired to utilize the mirror p qof extended form,' both calculation and experience show vthat it wouldbe necessary to utilize either another process of manufacture than workformed in relief, or to use some material other than silvered brass forthe making of said mirror since the variations of radii of curvature'practically obtainable between the theoretical shape of t-he mirror andthe form realized by the relief work of the brass being about one Smillimetre, there may result starting from the vpoint p, displacementsof the upper foci greater than two millimetres and the obtention ofrefiected rays, originating from rays emitted by the source of light iy' which depart from the axis D E. A

This is why after having constructed at p the normal to the parabola pg, there is selected upon this normal p 7', a point 'r which 95 is suchthat by taking this point as a centre, and half the length of p 7" asradius the curve described does not meet the rectangle Z m n o thispoint rbeing selected as the centre of a spherical mirror of silveredbrass having the 10o radius p 7*, by which the mirror p g is prolongedup to the straight-line D E.. h

Theoretically and practically this mirror will reflect towards the axisD E all the luminous rays 7c s, for example, emitted by the source z' jla and impinging thereon.

Underneath the source of light there is arranged a second parabolic`mirror u e of brass silvered and polished, the optical axis of whichcoincides withthe straight line D E, and of which the focus is at Forthe reasons hereinbefore set forth starting from the point u, thismirror isextended up to the straight line D E by a' spherical mirror u whavingv a centre fr and of which the radius is u, the mirror being suchthat the point w is at the intersection of the normal u to the parabolau lu and the straight line D E. -As

may be seen, the curve has for its centre the point and the curveproduced by taking half the radius 'afu does not encounter the rectangleZ m n o. The spherical curve u lw is prolonged up .to the line or axis DE. p

The luminous rays emitted from the source of light 1I j c, the rays z' vand z' w, for example, meet the mirror 'u u w and will be reflectedthereby so that they depart from the axis D E.

The curvature of the mirrors g p s and v u 'w being fixed in the mannerjust described the reflecting surfaces to be utilized will be obtainedby rotation of the curves g p s and 'v u lw round the straight line D Etaken as axis, and causing each of these curves to make a rotation of 90degrees on both sides of the plane in which they lie.

The reflector therefore consists of an upper and a lower parthaving acommon axis D E, of which the upper part comprises an outer parabolicsurface o g having its focus o 'on the common axis D E and an innerspherical surfacep s forming a continuation of the parabolic surface andhaving its center r and its focus below the axis. The lower partcomprises similar surfaces, of which the outer parabolic surface u lvhas its focus n on the common axis D E and in front of thefocusio-oftheupper parabolic surface p g and an inner spherical surface'v fw forming a continuation of the lower parabolic surface havingitscenter m, on the common axis and its focus therebelow. a

It is, of course, understood that the reflector can be reversed, inwhich case reference to the points and surfaces above and below axis D Eare reversed. Y

What I claim as my invention and desire to secure by Letters Patent ofthe United States is A refiector consisting of an upper and a lower'parthaving substantially a common axis, the upper part comprising an outerparabolic surface having its focus on the common axis and an innerspherlcal surface forming a contmuatlonof the parabolic surface andcation.

JACQUES LOUIS PECH.

